Vertical integration scheme and circuit elements architecture for area scaling of semiconductor devices

ABSTRACT

Vertical integration schemes and circuit elements architectures for area scaling of semiconductor devices are described. In an example, an inverter structure includes a semiconductor fin separated vertically into an upper region and a lower region. A first plurality of gate structures is included for controlling the upper region of the semiconductor fin. A second plurality of gate structures is included for controlling the lower region of the semiconductor fin. The second plurality of gate structures has a conductivity type opposite the conductivity type of the first plurality of gate structures.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductor devicesand processing and, in particular, vertical integration schemes andcircuit elements architectures for area scaling of semiconductordevices.

BACKGROUND

For the past several decades, the scaling of features in integratedcircuits has been a driving force behind an ever-growing semiconductorindustry. Scaling to smaller and smaller features enables increaseddensities of functional units on the limited real estate ofsemiconductor chips. For example, shrinking transistor size allows forthe incorporation of an increased number of memory or logic devices on achip, lending to the fabrication of products with increased capacity.The drive for ever-more capacity, however, is not without issue. Thenecessity to optimize the performance of each device becomesincreasingly significant.

In the manufacture of integrated circuit devices, multi-gatetransistors, such as tri-gate transistors, have become more prevalent asdevice dimensions continue to scale down. In conventional processes,tri-gate transistors are generally fabricated on either bulk siliconsubstrates or silicon-on-insulator substrates. In some instances, bulksilicon substrates are preferred due to their lower cost and becausethey enable a less complicated tri-gate fabrication process.

Scaling multi-gate transistors has not been without consequence,however. As the dimensions of these fundamental building blocks ofmicroelectronic circuitry are reduced and as the sheer number offundamental building blocks fabricated in a given region is increased,the constraints on the lithographic processes used to pattern thesebuilding blocks have become overwhelming. In particular, there may be atrade-off between the smallest dimension of a feature patterned in asemiconductor stack (the critical dimension) and the spacing betweensuch features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plan view of a layout including fin-basedsemiconductor devices accommodating end-to-end spacing, in accordancewith the prior art.

FIGS. 2A and 2B illustrate cross-sectional views of an inverter circuitelement fabricated using a single semiconductor fin structure, inaccordance with an embodiment of the present invention.

FIGS. 3A and 3B illustrate cross-sectional views of a pass gate circuitelement fabricated using a single semiconductor fin structure, inaccordance with an embodiment of the present invention.

FIGS. 4A and 4B illustrate cross-sectional views of an AND gate circuitelement fabricated using a single semiconductor fin structure, inaccordance with an embodiment of the present invention.

FIGS. 5A and 5B illustrate cross-sectional views of an OR gate circuitelement fabricated using a single semiconductor fin structure, inaccordance with an embodiment of the present invention.

FIGS. 6A and 6B illustrate cross-sectional views of a circuit elementbased on two parallel PMOS devices fabricated using a singlesemiconductor fin structure as a component of a NAND gate circuitelement, in accordance with an embodiment of the present invention.

FIGS. 7A and 7B illustrate cross-sectional views of a circuit elementbased on two serial NMOS devices fabricated using a single semiconductorfin structure as a component of a NAND gate circuit element for couplingwith the two parallel PMOS devices of FIGS. 6A and 6B, in accordancewith an embodiment of the present invention.

FIGS. 8A and 8B illustrate cross-sectional views of a circuit elementbased on two parallel NMOS devices fabricated using a singlesemiconductor fin structure as a component of a NOR gate circuitelement, in accordance with an embodiment of the present invention.

FIGS. 8C and 8D illustrate cross-sectional views of a circuit elementbased on two serial PMOS devices fabricated using a single semiconductorfin structure as a component of a NOR gate circuit element for couplingwith the two parallel NMOS devices of FIGS. 8A and 8B, in accordancewith an embodiment of the present invention.

FIGS. 9-20 illustrate cross-sectional views of various operations forfabricating an inverter structure (left-hand-side of each of FIGS. 9-20)and a pass gate structure (right-hand-side of each of FIGS. 9-20), inaccordance with an embodiment of the present invention.

FIGS. 21 and 22 are cross-sectional views representing variousoperations in a layer transfer technology that may be implemented tofabricate an initial base stack for a fin structure, in accordance withan embodiment of the present invention.

FIG. 23 illustrates cross-sectional views of finalized devicesfabricated either on (a) a silicon substrate or (b) a buried oxidesubstrate, in accordance with an embodiment of the present invention.

FIG. 24 illustrates cross-sectional views of finalized devicesfabricated with underlying routing layers, in accordance with anembodiment of the present invention.

FIG. 25 illustrates an example of power being transferred from one sideof a device to the opposite side, in accordance with an embodiment ofthe present invention.

FIG. 26 illustrates a cross-sectional view of vertically integratedsingle fin elements having interconnect wiring between device layers, inaccordance with an embodiment of the present invention.

FIG. 27 illustrates an approach for extending the above principles to afour device structure technique, in accordance with an embodiment of thepresent invention.

FIG. 28A illustrates a cross-sectional view of a non-planarsemiconductor device having a vertical architecture and self-alignedgate edge isolation, in accordance with an embodiment of the presentinvention.

FIG. 28B illustrates a plan view taken along the a-a′ axis of thesemiconductor device of FIG. 28A, in accordance with an embodiment ofthe present invention.

FIG. 29 illustrates a computing device in accordance with oneimplementation of the invention.

FIG. 30 is an interposer implementing one or more embodiments of theinvention.

DESCRIPTION OF THE EMBODIMENTS

Vertical integration schemes and circuit elements architectures for areascaling of semiconductor devices are described. In the followingdescription, numerous specific details are set forth, such as specificintegration and material regimes, in order to provide a thoroughunderstanding of embodiments of the present invention. It will beapparent to one skilled in the art that embodiments of the presentinvention may be practiced without these specific details. In otherinstances, well-known features, such as integrated circuit designlayouts, are not described in detail in order to not unnecessarilyobscure embodiments of the present invention. Furthermore, it is to beunderstood that the various embodiments shown in the Figures areillustrative representations and are not necessarily drawn to scale.

One or more embodiments of the present invention are directed to avertical integration scheme and circuit elements architecture for 2×area scaling for reduced layout usage. In an embodiment, an entirecircuit element is fabricated based on a single semiconductor fin, asopposed to fabricating one transistor per fin which is then tied into acircuit element. Some of the circuit elements described herein are builtwithin the framework of a boxed in device, such as a framework based ongate edge structures (e.g., as gate isolation regions) of gateelectrodes of the semiconductor structures or devices. In one or moreembodiments, devices described herein are fabricated for SRAM or likearchitectures based on complementary metal oxide semiconductor (CMOS)devices.

To provide context, increasing transistor density helps increase thenumber of transistors per chip or number of chips per wafer. It isbecoming very difficult to scale transistor pitch. One or moreembodiments described herein enable significant chip area scaling ortransistor density increase (2×) by vertically integrating transistorsto manufacture circuit elements (e.g., inverters/NAND/NOR/AND/OR gatesand SRAM cells). For stacking two device layers, architectures describedherein have advantages over sequential device fabrication. First, themost expensive front end patterning layers (e.g., poly and fin) do notneed to be performed twice. Second, if metal interconnect layers betweendevices are not required, such an architecture locates the devices muchcloser to one another. In one embodiment, a very compact CMOS elementarycircuit is achieved.

To provide further context, scaling of gate endcap and trench contact(TCN) endcap regions are important contributors towards improvingtransistor layout area and density. Gate and TCN endcap regions refer togate and TCN overlap of the diffusion region/fins of semiconductordevices. As an example, FIG. 1 illustrates a plan view of a layout 100including fin-based semiconductor devices accommodating end-to-endspacing, in accordance with the prior art. Referring to FIG. 1, first102 and second 104 semiconductor devices are based on semiconductor fins106 and 108, respectively. Each device 102 and 104 has a gate electrode110 or 112, respectively. Additionally, each device 102 and 104 hastrench contacts (TCNs) 114 and 116, respectively, at source and drainregions of the fins 106 and 108, respectively. The gate electrodes 110and 112 and the TCNs 114 and 116 each have an end cap region, which islocated off of the corresponding fins 106 and 108, respectively.

Referring again to FIG. 1, typically, gate and TCN endcap dimensionsmust include an allowance for mask registration error to ensure robusttransistor operation for worst case mask mis-registration, leaving anend-to-end spacing 118. Thus, another important design rule critical toimproving transistor layout density is the spacing between two adjacentendcaps facing each other. However, the parameters of“2*Endcap+End-to-End Spacing” are becoming increasingly difficult toscale using lithographic patterning to meet the scaling requirements fornew technologies. In particular, the additional endcap length requiredto allow for mask registration error also increases gate capacitancevalues due to longer overlap length between TCN and gate electrodes,thereby increasing product dynamic energy consumption and degradingperformance. Previous solutions have focused on improving registrationbudget and patterning or resolution improvements to enable shrinkage ofboth endcap dimension and endcap-to-endcap spacing.

In accordance with an embodiment of the present invention, approachesare described which provide for self-aligned gate endcap (SAGE) and TCNoverlap of a semiconductor fin without any need to allow for maskregistration. Although not so limited, one or more embodiments may beimplemented within a SAGE framework, which is an example of a boxed inapproach. In an embodiment, circuit elements are fabricated in each fininstead of just one transistor being fabricated in a single fin. With orwithout a further size controlling framework such as SAGE, one or moreembodiments described herein involve fabrication of an entire circuitelement based on single fin.

In a first example of a circuit element that may be fabricated using asingle fin, FIGS. 2A and 2B illustrate cross-sectional views of aninverter circuit element fabricated using a single semiconductor finstructure, in accordance with an embodiment of the present invention.FIG. 2A is a cross-sectional view taken through the gate structures andalong the fin structure. FIG. 2B is a cross-sectional view taken throughthe fin structure and along the gate structures.

Referring to FIG. 2A, a semiconductor fin 202 can be viewed as beingseparated vertically into an upper region 202A and a lower region 202B.In one embodiment, the upper region 202A and the lower region 202B ofthe semiconductor fin 202 are separated by an insulating layer 204, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The insulating layer 204 may include regions 204A and204B of differing insulating material, depending on the integrationscheme used to fabricate the structure, examples of which are describedin greater detail below.

A first plurality of gate structures 206, such as PMOS gate structures,is included above the upper region 202A of the semiconductor fin 202.Each of the first plurality of gate structures 206 can include a gateelectrode 208, a gate dielectric layer 210 and associated dielectricspacers 212. It is to be appreciated that the first plurality of gatestructures 206 extends from the top of the upper region 202A of thesemiconductor fin 202 (as shown) and further wraps the upper region 202Aof the semiconductor fin 202 at locations into and out of the page withrespect to the perspective shown in FIG. 2A. The upper region 202A ofthe semiconductor fin 202 may, in an embodiment, further include regrownsource or drain regions. In an exemplary embodiment, the upper region202A of the semiconductor fin 202 further includes epitaxial P-typesilicon germanium regions 214, leaving remaining semiconductor regions(such as silicon regions) 216 of the upper region 202A of thesemiconductor fin 202.

Although not depicted in FIG. 2A, but is shown in FIG. 2B, the lowerregion 202B of the semiconductor fin 202 is associated with a secondplurality of gate structures 218, such as NMOS gate structures. Each ofthe second plurality of gate structures 218 can include a gate electrode220, a gate dielectric layer 222 and associated dielectric spacers. Itis to be appreciated that the second plurality of gate structures 218wraps the lower region 202B of the semiconductor fin 202 at locationsinto and out of the page with respect to the perspective shown in FIG.2A and, thus, can only be seen in the cross-sectional view of FIG. 2B,i.e., at regions 218A. As shown in FIG. 2B, in a specific embodimentwhere the semiconductor structure is a nanowire structure, each of thesecond plurality of gate structures 218 further wraps below the lowerregion 202B of the semiconductor fin 202 at locations 218B. However, inanother embodiment, in the case of a fin structure that is a bulk finstructure or is otherwise coupled to an underlying substrate, portions218B of each of the second plurality of gate structures 218 are notincluded, such that a tri-gate like structure is formed.

Referring again to FIG. 2A, in an embodiment, the lower region 202B ofthe semiconductor fin 202 may further include regrown source or drainregions. In an exemplary embodiment, the lower region 202B of thesemiconductor fin 202 further includes epitaxial N-type silicon regions226, leaving remaining semiconductor regions (such as silicon regions)228 of the lower region 202B of the semiconductor fin 202.

In an embodiment, each of the first plurality of gate structures 206 isformed in a same trench as a corresponding one of the second pluralityof gate structures 218, but vertically above the corresponding one ofthe second plurality of gate structures 218. In one such embodiment,each of the first plurality of gate structures 206 is isolated from thecorresponding one of the second plurality of gate structures 218 by aninsulating layer 224, as is depicted in FIG. 2B. However, in anotherembodiment, each of the first plurality of gate structures 206 forms aP/N junction with the corresponding one of the second plurality of gatestructures 218 to effectively connect or short together certain of thegate pairings.

Referring again to FIGS. 2A and 2B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 230 contacts a first upper region214 and a first lower region 226 to form a Vout contact. A secondconductive contact 232 contacts a second upper region 214 to form a Vcccontact. Finally, a third conductive contact 234 contacts a second lowerregion 226 to form a contact to ground (GND).

Referring again to FIGS. 2A and 2B, an entire inverter structure isfabricated on a single fin 202. That is, an entire circuit element isfabricated on a single semiconductor fin. It is to be appreciated thatin order to use such an inverter to fabricate an SRAM cell, two suchinverters can be coupled with two pass gates. In accordance with anembodiment of the present invention, each such pass gate is alsofabricated on a single fin.

In a second example of a circuit element that may be fabricated using asingle fin, FIGS. 3A and 3B illustrate cross-sectional views of a passgate circuit element fabricated using a single semiconductor finstructure, in accordance with an embodiment of the present invention.FIG. 3A is a cross-sectional view taken through the gate structures andalong the fin structure. FIG. 3B is a cross-sectional view taken throughthe fin structure and along the gate structures.

Referring to FIG. 3A, a semiconductor fin 302 can be viewed as beingseparated vertically into an upper region 302A and a lower region 302B.In one embodiment, the upper region 302A and the lower region 302B ofthe semiconductor fin 302 are separated by an insulating layer 304, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The insulating layer 304 may include regions 304A and304B of differing insulating material, depending on the integrationscheme used to fabricate the structure, examples of which are describedin greater detail below.

A first plurality of gate structures 306, such as NMOS gate structures,is included above the upper region 302A of the semiconductor fin 302.Each of the first plurality of gate structures 306 can include a gateelectrode 308, a gate dielectric layer 310 and associated dielectricspacers 312. It is to be appreciated that the first plurality of gatestructures 306 extends from the top of the upper region 302A of thesemiconductor fin 302 (as shown) and further wraps the upper region 302Aof the semiconductor fin 302 at locations into and out of the page withrespect to the perspective shown in FIG. 3A. The upper region 302A ofthe semiconductor fin 302 may, in an embodiment, further include regrownsource or drain regions. In an exemplary embodiment, the upper region302A of the semiconductor fin 302 further includes first epitaxialN-type silicon regions 314, leaving remaining semiconductor regions(such as silicon regions) 316 of the upper region 302A of thesemiconductor fin 302.

Although not depicted in FIG. 3A, but is shown in FIG. 3B, the lowerregion 302B of the semiconductor fin 302 is associated with a secondplurality of gate structures 318, such as a second plurality of NMOSgate structures. Each of the second plurality of gate structures 318 caninclude a gate electrode 320, a gate dielectric layer 322 and associateddielectric spacers. It is to be appreciated that the second plurality ofgate structures 318 wraps the lower region 302B of the semiconductor fin302 at locations into and out of the page with respect to theperspective shown in FIG. 3A and, thus, can only be seen in thecross-sectional view of FIG. 3B, i.e., at regions 318A. As shown in FIG.3B, in a specific embodiment where the semiconductor structure is ananowire structure, each of the second plurality of gate structures 318further wraps below the lower region 302B of the semiconductor fin 302at locations 318B. However, in another embodiment, in the case of a finstructure that is a bulk fin structure or is otherwise coupled to anunderlying substrate, portions 318B of each of the second plurality ofgate structures 318 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 3A, in an embodiment, the lower region 302B ofthe semiconductor fin 302 may further include regrown source or drainregions. In an exemplary embodiment, the lower region 302B of thesemiconductor fin 302 further includes epitaxial N-type silicon regions326, leaving remaining semiconductor regions (such as silicon regions)328 of the lower region 302B of the semiconductor fin 302.

In an embodiment, each of the first plurality of gate structures 306 isformed in a same trench as a corresponding one of the second pluralityof gate structures 318, but vertically above the corresponding one ofthe second plurality of gate structures 318. In one such embodiment,each of the first plurality of gate structures 306 has a sameconductivity type (e.g., N-type) and is isolated from the correspondingone of the second plurality of gate structures 318 by an insulatinglayer 324, as is depicted in FIG. 3B.

Referring again to FIGS. 3A and 3B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 330 contacts a first upper region314 to form a connection to a first inverter element. A secondconductive contact 332 contacts a first lower region 326 to form aconnection to a second inverter element. A third conductive contact 334contacts a second upper region 314 to form a first bitline contact.Finally, a fourth conductive contact 336 contacts a second lower region326 to form a second bitline contact. Thus, an entire pass gatestructure is fabricated on a single fin 302.

It is to be appreciated that current solutions involve decreasing polypitch and fin pitch which puts tremendous constraint on processtechnology to etch/deposit/and perform lithography in ever smallerdimensions. By contrast, embodiments described herein allow transistordensity increase without drawn pitch scaling. Embodiments may involveapplication of such an approach to AND gates (e.g., FIGS. 4A and 4B), ORgates (e.g., FIGS. 5A and 5B), NAND architectures (e.g., FIGS. 6A, 6B,7A and 7B), NOR architectures (e.g., FIGS. 8A-8D), inverters (e.g.,FIGS. 2A and 2B), SRAM cells (e.g., FIGS. 2A, 2B, 3A and 3B) and otherrandom logic components.

In a third example of a circuit element that may be fabricated using asingle fin, FIGS. 4A and 4B illustrate cross-sectional views of an ANDgate circuit element fabricated using a single semiconductor finstructure, in accordance with an embodiment of the present invention.FIG. 4A is a cross-sectional view taken through the gate structures andalong the fin structure. FIG. 4B is a cross-sectional view taken throughthe fin structure and along the gate structures.

Referring to FIG. 4A, a semiconductor fin 402 can be viewed as beingseparated vertically into an upper region 402A and a lower region 402B.In one embodiment, the upper region 402A and the lower region 402B ofthe semiconductor fin 402 are separated by an insulating layer 404, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The insulating layer 404 may include regions 404A and404B of differing insulating material, depending on the integrationscheme used to fabricate the structure, examples of which are describedin greater detail below.

A first plurality of gate structures 406, such as NMOS gate structures,is included above the upper region 402A of the semiconductor fin 402.Each of the first plurality of gate structures 406 can include a gateelectrode 408, a gate dielectric layer 410 and associated dielectricspacers 412. It is to be appreciated that the first plurality of gatestructures 406 extends from the top of the upper region 402A of thesemiconductor fin 402 (as shown) and further wraps the upper region 402Aof the semiconductor fin 402 at locations into and out of the page withrespect to the perspective shown in FIG. 4A. The upper region 402A ofthe semiconductor fin 402 may, in an embodiment, further include regrownsource or drain regions. In an exemplary embodiment, the upper region402A of the semiconductor fin 402 further includes first epitaxialN-type silicon regions 414, leaving remaining semiconductor regions(such as silicon regions) 416 of the upper region 402A of thesemiconductor fin 402.

Although not depicted in FIG. 4A, but is shown in FIG. 4B, the lowerregion 402B of the semiconductor fin 402 is associated with a secondplurality of gate structures 418, such as a second plurality of NMOSgate structures. Each of the second plurality of gate structures 418 caninclude a gate electrode 420, a gate dielectric layer 422 and associateddielectric spacers. It is to be appreciated that the second plurality ofgate structures 418 wraps the lower region 402B of the semiconductor fin402 at locations into and out of the page with respect to theperspective shown in FIG. 4A and, thus, can only be seen in thecross-sectional view of FIG. 4B, i.e., at regions 418A. As shown in FIG.4B, in a specific embodiment where the semiconductor structure is ananowire structure, each of the second plurality of gate structures 418further wraps below the lower region 402B of the semiconductor fin 402at locations 418B. However, in another embodiment, in the case of a finstructure that is a bulk fin structure or is otherwise coupled to anunderlying substrate, portions 418B of each of the second plurality ofgate structures 418 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 4A, in an embodiment, the lower region 402B ofthe semiconductor fin 402 may further include regrown source or drainregions. In an exemplary embodiment, the lower region 402B of thesemiconductor fin 402 further includes epitaxial N-type silicon regions426, leaving remaining semiconductor regions (such as silicon regions)428 of the lower region 402B of the semiconductor fin 402.

In an embodiment, each of the first plurality of gate structures 406 isformed in a same trench as a corresponding one of the second pluralityof gate structures 418, but vertically above the corresponding one ofthe second plurality of gate structures 418. In one such embodiment,each of the first plurality of gate structures 406 has a sameconductivity type (e.g., N-type) and is isolated from the correspondingone of the second plurality of gate structures 418 by an insulatinglayer 424, as is depicted in FIG. 4B.

Referring again to FIGS. 4A and 4B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 430 contacts a first upper region414 and a first lower region 426 to form a contact. A second conductivecontact 432 contacts a second upper region 414 to form an OUT terminal.Finally, a third conductive contact 434 contacts a second lower region426 to form a contact to ground (GND). Thus, an entire AND gatestructure is fabricated on a single fin 402.

In a fourth example of a circuit element that may be fabricated using asingle fin, FIGS. 5A and 5B illustrate cross-sectional views of an ORgate circuit element fabricated using a single semiconductor finstructure, in accordance with an embodiment of the present invention.FIG. 5A is a cross-sectional view taken through the gate structures andalong the fin structure. FIG. 5B is a cross-sectional view taken throughthe fin structure and along the gate structures.

Referring to FIG. 5A, a semiconductor fin 502 can be viewed as beingseparated vertically into an upper region 502A and a lower region 502B.In one embodiment, the upper region 502A and the lower region 502B ofthe semiconductor fin 502 are separated by an insulating layer 504, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The insulating layer 504 may include regions 504A and504B of differing insulating material, depending on the integrationscheme used to fabricate the structure, examples of which are describedin greater detail below.

A first plurality of gate structures 506, such as NMOS gate structures,is included above the upper region 502A of the semiconductor fin 502.Each of the first plurality of gate structures 506 can include a gateelectrode 508, a gate dielectric layer 510 and associated dielectricspacers 512. It is to be appreciated that the first plurality of gatestructures 506 extends from the top of the upper region 502A of thesemiconductor fin 502 (as shown) and further wraps the upper region 502Aof the semiconductor fin 502 at locations into and out of the page withrespect to the perspective shown in FIG. 5A. The upper region 502A ofthe semiconductor fin 502 may, in an embodiment, further include regrownsource or drain regions. In an exemplary embodiment, the upper region502A of the semiconductor fin 502 further includes first epitaxialN-type silicon regions 514, leaving remaining semiconductor regions(such as silicon regions) 516 of the upper region 502A of thesemiconductor fin 502.

Although not depicted in FIG. 5A, but is shown in FIG. 5B, the lowerregion 502B of the semiconductor fin 502 is associated with a secondplurality of gate structures 518, such as a second plurality of NMOSgate structures. Each of the second plurality of gate structures 518 caninclude a gate electrode 520, a gate dielectric layer 522 and associateddielectric spacers. It is to be appreciated that the second plurality ofgate structures 518 wraps the lower region 502B of the semiconductor fin502 at locations into and out of the page with respect to theperspective shown in FIG. 5A and, thus, can only be seen in thecross-sectional view of FIG. 5B, i.e., at regions 518A. As shown in FIG.5B, in a specific embodiment where the semiconductor structure is ananowire structure, each of the second plurality of gate structures 518further wraps below the lower region 502B of the semiconductor fin 502at locations 518B. However, in another embodiment, in the case of a finstructure that is a bulk fin structure or is otherwise coupled to anunderlying substrate, portions 518B of each of the second plurality ofgate structures 518 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 5A, in an embodiment, the lower region 502B ofthe semiconductor fin 502 may further include regrown source or drainregions. In an exemplary embodiment, the lower region 502B of thesemiconductor fin 502 further includes epitaxial N-type silicon regions526, leaving remaining semiconductor regions (such as silicon regions)528 of the lower region 502B of the semiconductor fin 502.

In an embodiment, each of the first plurality of gate structures 506 isformed in a same trench as a corresponding one of the second pluralityof gate structures 518, but vertically above the corresponding one ofthe second plurality of gate structures 518. In one such embodiment,each of the first plurality of gate structures 506 has a sameconductivity type (e.g., N-type) and is isolated from the correspondingone of the second plurality of gate structures 518 by an insulatinglayer 524, as is depicted in FIG. 5B.

Referring again to FIGS. 5A and 5B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 530 contacts a first upper region514 and a first lower region 526. A second conductive contact 532contacts a second upper region 514 and a second lower region 526. Thus,an entire OR gate structure is fabricated on a single fin 502.

NAND gate architectures can be divided into two parallel PMOS (e.g.,FIGS. 6A and 6B) with output node connected to two serial NMOS (e.g.,FIGS. 7A and 7B), as described below.

In a fifth example of a circuit element that may be fabricated using asingle fin, FIGS. 6A and 6B illustrate cross-sectional views of acircuit element based on two parallel PMOS devices fabricated using asingle semiconductor fin structure as a component of a NAND gate circuitelement, in accordance with an embodiment of the present invention. FIG.6A is a cross-sectional view taken through the gate structures and alongthe fin structure. FIG. 6B is a cross-sectional view taken through thefin structure and along the gate structures.

Referring to FIG. 6A, a semiconductor fin 602 can be viewed as beingseparated vertically into an upper region 602A and a lower region 602B.In one embodiment, the upper region 602A and the lower region 602B ofthe semiconductor fin 602 are separated by an insulating layer 604, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The semiconductor fin 602 may be further disposed on aninsulating layer 603, such as an oxide layer, as is depicted in FIG. 6A.

A first plurality of PMOS gate structures 606 is included above theupper region 602A of the semiconductor fin 602. Each of the firstplurality of PMOS gate structures 606 can include a gate electrode 608,a gate dielectric layer 610 and associated dielectric spacers 612. It isto be appreciated that the first plurality of PMOS gate structures 606extends from the top of the upper region 602A of the semiconductor fin602 (as shown) and further wraps the upper region 602A of thesemiconductor fin 602 at locations into and out of the page with respectto the perspective shown in FIG. 6A.

Although not depicted in FIG. 6A, but is shown in FIG. 6B, the lowerregion 602B of the semiconductor fin 602 is associated with a secondplurality of PMOS gate structures 618. Each of the second plurality ofPMOS gate structures 618 can include a gate electrode 620, a gatedielectric layer 622 and associated dielectric spacers. It is to beappreciated that the second plurality of PMOS gate structures 618 wrapsthe lower region 602B of the semiconductor fin 602 at locations into andout of the page with respect to the perspective shown in FIG. 6A and,thus, can only be seen in the cross-sectional view of FIG. 6B, i.e., atregions 618A. As shown in FIG. 6B, in a specific embodiment where thesemiconductor structure is a nanowire structure, each of the secondplurality of PMOS gate structures 618 further wraps below the lowerregion 602B of the semiconductor fin 602 at locations 618B. However, inanother embodiment, in the case of a fin structure that is a bulk finstructure or is otherwise coupled to an underlying substrate or theoxide layer 603, portions 618B of each of the second plurality of PMOSgate structures 618 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 6A, in an embodiment, both the upper region 602Aand the lower region 602B of the semiconductor fin 602 may furtherinclude regrown source or drain regions. In an exemplary embodiment,both the upper region 602A and the lower region 602B of thesemiconductor fin 602 further include epitaxial P-type silicon germaniumregions 626, leaving remaining semiconductor regions (such as siliconregions) 628 of the semiconductor fin 602.

In an embodiment, each of the first plurality of PMOS gate structures606 is formed in a same trench as a corresponding one of the secondplurality of PMOS gate structures 618, but vertically above thecorresponding one of the second plurality of PMOS gate structures 618.In one such embodiment, each of the first plurality of PMOS gatestructures 606 is isolated from the corresponding one of the secondplurality of PMOS gate structures 618 by an insulating layer 624, as isdepicted in FIG. 6B.

Referring again to FIGS. 6A and 6B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 630 contacts a first epitaxialP-type silicon germanium region 626 to form a Vcc contact. A secondconductive contact 632 contacts a second epitaxial P-type silicongermanium region 626 to form a Vout contact.

In a sixth example of a circuit element that may be fabricated using asingle fin, FIGS. 7A and 7B illustrate cross-sectional views of acircuit element based on two serial NMOS devices fabricated using asingle semiconductor fin structure as a component of a NAND gate circuitelement for coupling with the two parallel PMOS devices of FIGS. 6A and6B, in accordance with an embodiment of the present invention. FIG. 7Ais a cross-sectional view taken through the gate structures and alongthe fin structure. FIG. 7B is a cross-sectional view taken through thefin structure and along the gate structures.

Referring to FIG. 7A, a semiconductor fin 702 can be viewed as beingseparated vertically into an upper region 702A and a lower region 702B.In one embodiment, the upper region 702A and the lower region 702B ofthe semiconductor fin 702 are separated by an insulating layer 704, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The semiconductor fin 702 may be further disposed on aninsulating layer 703, such as an oxide layer, as is depicted in FIG. 7A.

A first plurality of NMOS gate structures 706 is included above theupper region 702A of the semiconductor fin 702. Each of the firstplurality of NMOS gate structures 706 can include a gate electrode 708,a gate dielectric layer 710 and associated dielectric spacers 712. It isto be appreciated that the first plurality of NMOS gate structures 706extends from the top of the upper region 702A of the semiconductor fin702 (as shown) and further wraps the upper region 702A of thesemiconductor fin 702 at locations into and out of the page with respectto the perspective shown in FIG. 7A.

Although not depicted in FIG. 7A, but is shown in FIG. 7B, the lowerregion 702B of the semiconductor fin 702 is associated with a secondplurality of NMOS gate structures 718. Each of the second plurality ofNMOS gate structures 718 can include a gate electrode 720, a gatedielectric layer 722 and associated dielectric spacers. It is to beappreciated that the second plurality of NMOS gate structures 718 wrapsthe lower region 702B of the semiconductor fin 702 at locations into andout of the page with respect to the perspective shown in FIG. 7A and,thus, can only be seen in the cross-sectional view of FIG. 7B, i.e., atregions 718A. As shown in FIG. 7B, in a specific embodiment where thesemiconductor structure is a nanowire structure, each of the secondplurality of NMOS gate structures 718 further wraps below the lowerregion 702B of the semiconductor fin 702 at locations 718B. However, inanother embodiment, in the case of a fin structure that is a bulk finstructure or is otherwise coupled to an underlying substrate or theoxide layer 703, portions 718B of each of the second plurality of NMOSgate structures 718 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 7A, in an embodiment, both the upper region 702Aand the lower region 702B of the semiconductor fin 702 may furtherinclude regrown source or drain regions. In an exemplary embodiment,both the upper region 702A and the lower region 702B of thesemiconductor fin 702 further include an epitaxial N-type silicon region726, leaving remaining semiconductor regions (such as silicon regions)728 of the semiconductor fin 702. Also, an upper epitaxial N-typesilicon region 727A is formed in only the upper region 702A of thesemiconductor fin 702, while a lower epitaxial N-type silicon region727B is formed in only the lower region 702B of the semiconductor fin702. The insulating layer portion 704B separates the upper epitaxialN-type silicon region 727A from the lower epitaxial N-type siliconregion 727B.

In an embodiment, each of the first plurality of NMOS gate structures706 is formed in a same trench as a corresponding one of the secondplurality of NMOS gate structures 718, but vertically above thecorresponding one of the second plurality of NMOS gate structures 718.In one such embodiment, each of the first plurality of NMOS gatestructures 706 is isolated from the corresponding one of the secondplurality of NMOS gate structures 718 by an insulating layer 724, as isdepicted in FIG. 7B.

Referring again to FIGS. 7A and 7B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 730 contacts the epitaxial N-typesilicon region 726. A second conductive contact 732 contacts the lowerepitaxial N-type silicon region 727B to form a Vout contact. A thirdconductive contact 734 contacts the upper epitaxial N-type siliconregion 727A to form a contact to ground (GND).

In a manner similar to the NAND architecture, NOR gate architecture canbe divided into two parallel NMOS (e.g., FIGS. 8A and 8B), output ofwhich is connected to output of two serial PMOS (e.g., FIGS. 8C and 8D),as is described below.

In a seventh example of a circuit element that may be fabricated using asingle fin, FIGS. 8A and 8B illustrate cross-sectional views of acircuit element based on two parallel NMOS devices fabricated using asingle semiconductor fin structure as a component of a NOR gate circuitelement, in accordance with an embodiment of the present invention. FIG.8A is a cross-sectional view taken through the gate structures and alongthe fin structure. FIG. 8B is a cross-sectional view taken through thefin structure and along the gate structures.

Referring to FIG. 8A, a semiconductor fin 802 can be viewed as beingseparated vertically into an upper region 802A and a lower region 802B.In one embodiment, the upper region 802A and the lower region 802B ofthe semiconductor fin 802 are separated by an insulating layer 804, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The semiconductor fin 802 may be further disposed on aninsulating layer 803, such as an oxide layer, as is depicted in FIG. 8A.

A first plurality of NMOS gate structures 806 is included above theupper region 802A of the semiconductor fin 802. Each of the firstplurality of NMOS gate structures 806 can include a gate electrode 808,a gate dielectric layer 810 and associated dielectric spacers 812. It isto be appreciated that the first plurality of NMOS gate structures 806extends from the top of the upper region 802A of the semiconductor fin802 (as shown) and further wraps the upper region 802A of thesemiconductor fin 802 at locations into and out of the page with respectto the perspective shown in FIG. 8A.

Although not depicted in FIG. 8A, but is shown in FIG. 8B, the lowerregion 802B of the semiconductor fin 802 is associated with a secondplurality of NMOS gate structures 818. Each of the second plurality ofNMOS gate structures 818 can include a gate electrode 820, a gatedielectric layer 822 and associated dielectric spacers. It is to beappreciated that the second plurality of NMOS gate structures 818 wrapsthe lower region 802B of the semiconductor fin 802 at locations into andout of the page with respect to the perspective shown in FIG. 8A and,thus, can only be seen in the cross-sectional view of FIG. 8B, i.e., atregions 818A. As shown in FIG. 8B, in a specific embodiment where thesemiconductor structure is a nanowire structure, each of the secondplurality of NMOS gate structures 818 further wraps below the lowerregion 802B of the semiconductor fin 802 at locations 818B. However, inanother embodiment, in the case of a fin structure that is a bulk finstructure or is otherwise coupled to an underlying substrate or theoxide layer 803, portions 818B of each of the second plurality of NMOSgate structures 818 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 8A, in an embodiment, both the upper region 802Aand the lower region 802B of the semiconductor fin 802 may furtherinclude regrown source or drain regions. In an exemplary embodiment,both the upper region 802A and the lower region 802B of thesemiconductor fin 802 further include epitaxial N-type silicon regions826, leaving remaining semiconductor regions (such as silicon regions)828 of the semiconductor fin 802.

In an embodiment, each of the first plurality of NMOS gate structures806 is formed in a same trench as a corresponding one of the secondplurality of NMOS gate structures 818, but vertically above thecorresponding one of the second plurality of NMOS gate structures 818.In one such embodiment, each of the first plurality of NMOS gatestructures 806 is isolated from the corresponding one of the secondplurality of NMOS gate structures 818 by an insulating layer 824, as isdepicted in FIG. 8B.

Referring again to FIGS. 8A and 8B, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 830 contacts a first epitaxialN-type silicon region 826 to form a ground (GND) contact. A secondconductive contact 832 contacts a second epitaxial N-type silicon region826 to form a Vout contact. It is to be appreciated that the contactscan be made either from the top or from the bottom on the devices,depending on how it is determined to deliver power.

In an eighth example of a circuit element that may be fabricated using asingle fin, FIGS. 8C and 8D illustrate cross-sectional views of acircuit element based on two serial PMOS devices fabricated using asingle semiconductor fin structure as a component of a NOR gate circuitelement for coupling with the two parallel NMOS devices of FIGS. 8A and8B, in accordance with an embodiment of the present invention. FIG. 8Cis a cross-sectional view taken through the gate structures and alongthe fin structure. FIG. 8D is a cross-sectional view taken through thefin structure and along the gate structures.

Referring to FIG. 8C, a semiconductor fin 852 can be viewed as beingseparated vertically into an upper region 852A and a lower region 852B.In one embodiment, the upper region 852A and the lower region 852B ofthe semiconductor fin 852 are separated by an insulating layer 854, suchas a silicon oxide layer or other insulating oxide layer or a siliconnitride layer. The semiconductor fin 852 may be further disposed on aninsulating layer 853, such as an oxide layer, as is depicted in FIG. 8C.

A first plurality of PMOS gate structures 856 is included above theupper region 852A of the semiconductor fin 852. Each of the firstplurality of PMOS gate structures 856 can include a gate electrode 858,a gate dielectric layer 860 and associated dielectric spacers 862. It isto be appreciated that the first plurality of PMOS gate structures 856extends from the top of the upper region 852A of the semiconductor fin852 (as shown) and further wraps the upper region 852A of thesemiconductor fin 852 at locations into and out of the page with respectto the perspective shown in FIG. 8C.

Although not depicted in FIG. 8C, but is shown in FIG. 8D, the lowerregion 852B of the semiconductor fin 852 is associated with a secondplurality of PMOS gate structures 868. Each of the second plurality ofPMOS gate structures 868 can include a gate electrode 870, a gatedielectric layer 872 and associated dielectric spacers. It is to beappreciated that the second plurality of PMOS gate structures 868 wrapsthe lower region 852B of the semiconductor fin 852 at locations into andout of the page with respect to the perspective shown in FIG. 8C and,thus, can only be seen in the cross-sectional view of FIG. 8D, i.e., atregions 868A. As shown in FIG. 8D, in a specific embodiment where thesemiconductor structure is a nanowire structure, each of the secondplurality of PMOS gate structures 868 further wraps below the lowerregion 852B of the semiconductor fin 852 at locations 868B. However, inanother embodiment, in the case of a fin structure that is a bulk finstructure or is otherwise coupled to an underlying substrate or theoxide layer 853, portions 868B of each of the second plurality of PMOSgate structures 868 are not included, such that a tri-gate likestructure is formed.

Referring again to FIG. 8C, in an embodiment, both the upper region 852Aand the lower region 852B of the semiconductor fin 852 may furtherinclude regrown source or drain regions. In an exemplary embodiment,both the upper region 852A and the lower region 852B of thesemiconductor fin 852 further include an epitaxial P-type silicongermanium region 876, leaving remaining semiconductor regions (such assilicon regions) 878 of the semiconductor fin 852. Also, an upperepitaxial P-type silicon germanium region 877A is formed in only theupper region 852A of the semiconductor fin 852, while a lower epitaxialP-type silicon germanium region 877B is formed in only the lower region852B of the semiconductor fin 852. The insulating layer portion 854Bseparates the upper epitaxial P-type silicon germanium region 877A fromthe lower epitaxial P-type silicon germanium region 877B.

In an embodiment, each of the first plurality of PMOS gate structures856 is formed in a same trench as a corresponding one of the secondplurality of PMOS gate structures 868, but vertically above thecorresponding one of the second plurality of PMOS gate structures 868.In one such embodiment, each of the first plurality of PMOS gatestructures 856 is isolated from the corresponding one of the secondplurality of PMOS gate structures 868 by an insulating layer 874, as isdepicted in FIG. 8D.

Referring again to FIGS. 8C and 8D, in an embodiment, wiringconsiderations such as backside wiring and wiring stacked between layersof semiconductor devices must be accounted for to bring the devices ofthe single fin together to form a circuit element. In one suchembodiment, a first conductive contact 880 contacts the epitaxial P-typesilicon germanium region 876. A second conductive contact 882 contactsthe lower epitaxial P-type silicon germanium region 877B to form a Vcccontact. A third conductive contact 884 contacts the upper epitaxialP-type silicon germanium region 877A to form a Vout contact. It is to beappreciated that the contacts can be made either from the top or fromthe bottom on the devices, depending on how it is determined to deliverpower.

In another aspect, in order to manufacture circuit elements instead of asingle transistor per corresponding fin, in an embodiment, isolation oftwo transistors for each fin is required. Tips and source/drain regionscan then be defined in the bottom transistor followed by contactformation in the bottom transistor. Subsequently, isolation of thebottom transistor from the top transistor is performed. Tips andsource/drain region are then formed for the top transistor.Subsequently, metal gates are fabricated for both the bottom and toptransistors, and contacts to the top transistor are formed. Contactformation for the top transistor can also be performed subsequent toforming metal gates for the top and bottom transistors. In an exemplaryembodiment, FIGS. 9-20 illustrate cross-sectional views of variousoperations for fabricating an inverter structure (left-hand-side of eachof FIGS. 9-20) and a pass gate structure (right-hand-side of each ofFIGS. 9-20), in accordance with an embodiment of the present invention.

Referring to FIG. 9, 900 is a cross-sectional view taken through thegate structures and along the fin structure, and 902 is across-sectional view taken through a source/drain region of the finstructure, in an operation in the fabrication of an inverter circuitelement. 904 is a cross-sectional view taken through the gate structuresand along the fin structure, and 906 is a cross-sectional view takenthrough a source/drain region of the fin structure, in an operation inthe fabrication of a pass gate circuit element.

Referring to part (a) of FIG. 9, a semiconductor fin 910 includes alower silicon layer 912 and an upper silicon layer 914. The lowersilicon layer 912 is separated from the upper silicon layer 914 by asilicon germanium layer 916. A plurality of dummy gate structures 918 isformed over the semiconductor fin 910, with source/drain locations 920between each of the plurality of dummy gate structures 918. Each of theplurality of dummy gate structures 918 may include a dummy gatedielectric layer 922 and a dummy gate electrode 924, as is depicted inFIG. 9.

Semiconductor fin 910 formation may begin with a starting structure ofblanket silicon/SiGe/silicon layers which is then etched to provide afin structure. A shallow trench isolation oxide may be formed adjacentlower regions of the etched fin stack. The plurality of dummy gatestructures 918 may form a grid pattern into and out of the page, and thepatterning may involve pitch halving or pitch quartering patterning.Additionally, it is to be appreciated that the plurality of dummy gatestructures 918 extends from the top of the upper silicon layer 914 ofthe semiconductor fin 910 (as shown) and further wraps the upper siliconlayer 914, the lower silicon layer 912, and the silicon germanium layer916 of the semiconductor fin 910 at locations into and out of the pagewith respect to the perspective shown in 900 and 904.

Referring to part (b) of FIG. 9, regions 926 of the silicon germaniumlayer 916 of the semiconductor fin 910 are removed. The regions 926correspond with source/drain locations 920. The regions 926 of thesilicon germanium layer 916 of the semiconductor fin 910 may be removedusing an etch process selective against etching of silicon.

Referring to FIG. 10, dielectric spacers 1000 are formed adjacent thesidewalls of each of the plurality of dummy gate structures 918. Thedielectric spacers 1000 may be fabricated by first forming a conformaldielectric layer on the structure of part (b) of FIG. 9 and thenanisotropically etching the conformal dielectric layer. In anembodiment, the dielectric material remains in the removed regions 926of the silicon germanium layer 916 to form dielectric regions 1002, asis depicted in FIG. 10.

Referring to FIG. 11, a vertical undercut etch is performed to removeportions of the semiconductor fin 910 from the source/drain locations920 to form undercut regions 1100. The width of the undercut feature maydepend on whether N-type or P-type semiconductor regions will ultimatelybe formed in the undercut regions 1100.

Referring to FIG. 12, epitaxial semiconductor regions 1200 are formed inthe undercut regions 1100 of the structure of FIG. 11. The epitaxialregions may be N-type (such as N-type silicon) or P-type (such as P-typesilicon germanium) regions, depending on the structural arrangementrequired. It is to be appreciated that growth from fin to fin may berestricted by an isolation wall 1202, as is used in a SAGE type process.

Referring to FIG. 13, the epitaxial semiconductor regions 1200 of thestructure of FIG. 12 are etched back to form lower epitaxialsource/drain regions 1300. Subsequently, dielectric spacers 1302 areformed above the lower epitaxial source/drain regions 1300. In anembodiment, the lower epitaxial source/drain regions 1300 are formed toa height at or below the height of the lower silicon layer 912 of thesemiconductor fin 910. The dielectric spacers 1302 may be sacrificialand may be used for ultimate fabrication of a self-aligned contact, asis described below.

Referring to FIG. 14, trench contacts 1400 are formed into the lowerepitaxial source/drain regions 1300 of the structure of FIG. 13 andwithin the dielectric spacers 1302. In an embodiment, the trenchcontacts 1400 ultimately provide contact to a lower transistorfabricated for the lower portion 912 of the semiconductor fin 910.

Referring to FIG. 15, the trench contacts 1400 of the structure of FIG.14 are recessed to provide lower contacts 1500. Also, the dielectricspacers 1302 may be removed at this stage, as is depicted in FIG. 15.

Referring to FIG. 16, an isolation oxide layer 1600 is then formed onthe lower contacts 1500 and the lower epitaxial source/drain regions1300 of the structure of FIG. 15. In an embodiment, the isolation oxidelayer 1600 is formed using an oxide fill, recess and wet cleanprocessing scheme. In an embodiment, the top of the isolation oxidelayer 1600 is approximately at the same level as the top of the silicongeranium layer 916 of the semiconductor fin 910. In an embodiment, theisolation oxide layer 1600 is ultimately used to isolate correspondingbottom and top transistors.

Referring to the inverter structure portion of FIG. 17, the uppersilicon layer 914 is undercut to form laterally recessed upper siliconlayer portions 914′. Epitaxial growth of upper source/drain regions 1700is then performed. In an embodiment, the lower transistor of theinverter structure is an NMOS device and the lower epitaxialsource/drain regions 1300 are N-type, such as N-type silicon regions. Inthat embodiment, the upper transistor of the inverter structure is aPMOS device and the upper epitaxial source/drain regions 1700 areP-type, such as P-type silicon germanium regions, as is depicted in FIG.17.

Referring to the pass gate portion of FIG. 17, epitaxial growth of uppersource/drain regions 1702 is performed. In an embodiment, the lowertransistor of the pass gate structure is an NMOS device and the lowerepitaxial source/drain regions 1300 are N-type, such as N-type siliconregions. In that embodiment, the upper transistor of the pass gatestructure is also an NMOS device and the upper epitaxial source/drainregions 1700 are N-type, such as N-type silicon regions, as is depictedin FIG. 17.

Referring to FIG. 18, a replacement gate process is then performed. Forexample, for the inverter structure, metal gate 1800 and high-k gatedielectric 1802 layers may be formed in place of the dummy gatestructures 918. Likewise, for the pass gate structure, metal gate 1804and high-k gate dielectric 1806 layers may be formed in place of thedummy gate structures 918.

In an embodiment, the replacement gate process is performed by formingan interlayer dielectric layer on the structure of FIG. 17. Such aninterlayer dielectric layer may then be polished down to expose apolysilicon layer (dummy gate electrode 924) for removal. During thisstage, remaining portions of the silicon germanium layer 916 are removedand replaced with an oxide fill material 1810, as is depicted in FIG.18. The oxide fill material 1810 ultimately isolates bottom and toptransistors. Subsequently, the lower transistor gate stack is formedwithin the trench formed upon removal of the dummy gate stack, which mayinvolve deposition and recessing of gate materials to a levelapproximately at the level of the lower silicon layer 912, on eitherside of the semiconductor fin 910 (i.e., into and out of the page of theperspective shown in FIG. 18.)

A top transistor gate material stack may then be formed above the lowertransistor gate material stack. In an embodiment, in the case of theinverter structure, the top transistor gate material stack is of anopposite conductivity type than that of the lower transistor gatematerial stack. In another embodiment, in the case of the pass gatestructure, the top transistor gate material stack is of a sameconductivity type as that of the lower transistor gate material stack.In either case, in an embodiment, within a same gate trench, anisolation layer is formed between the lower transistor gate materialstack and the top transistor gate material stack. A portion of the toptransistor gate stack is shown as 1800/1802 for the inverter structureand as 1804/1806 for the pass gate structure. It is to be appreciatedthat additional portions of the top transistor gate stack are alsoformed to a level approximately at the lower level of the upper siliconlayer 914, on either side of the semiconductor fin 910 (i.e., into andout of the page of the perspective shown in FIG. 18.)

Referring to FIG. 19, a dielectric spacer 1900 is then formed.Dielectric spacer 1900 may be formed by first depositing a blanket filmfollowed by contact lithography to open areas where top and bottomtransistors are to be connected. A spacer dry etch may then be performedto form dielectric spacers 1900. Additionally, in select locations,epitaxial semiconductor dry etch (e.g., for one of the regions 1700) maythen be performed to extend contact region 1902 where a top and bottomtransistor are to be electrically connected.

Referring to FIG. 20, upper contacts 2000 are then formed. In oneembodiment, one contact 2002 of the upper contacts is electricallyconnected to one of the lower contacts 1500, as is the case for theinverter structure of FIG. 20. The upper contacts may be fabricated bystripping a photoresist, followed by a blanket contact etch fabricationscheme to form required source/drain connections between top and bottomtransistors.

Similarly, NAND gate fabrication using two fins can be formed byconnecting two parallel PMOS on fin1 (e.g., FIGS. 6A and 6B) and twoserial NMOS on fin2 (e.g., FIGS. 7A and 7B). It is to be appreciatedthat the parallel PMOS have separate source/drain with no connectionbetween top and bottom transistors. In an embodiment, serial NMOS can beformed by one source/drain (either on left, or right) connected betweentop and bottom transistors and the other source/drain isolated betweentop and bottom.

In an embodiment, NOR gate architecture can be formed like NAND gatearchitecture by processing parallel NMOS transistors and serial PMOStransistors. Other elements of logic gates, or random logic and someelements of sequential logic can also be combined and made vertically ona single fin, using process steps mentioned above. Furthermore,combining this approach with routing tracks underneath the devices canyield complex gates in small areas. Additionally, total drive of thecircuit elements can be increased by using multiple fins.

In an embodiment, a vertical architecture can alternatively beconstructed using layer transfer technology, either at full device levelor at the fin level. In addition, the semiconductor materials do notnecessarily need to be Si, but can be any appropriate semiconductingmaterial depending on the application. For example, FIGS. 21 and 22 arecross-sectional views representing various operations in a layertransfer technology that may be implemented to fabricate an initial basestack for a fin structure, in accordance with an embodiment of thepresent invention.

Referring to FIG. 21, a base stack 2100 includes a first semiconductorlayer 2102, a first oxide layer 2104, a second semiconductor layer 2106and a second oxide layer 2108, all formed on an underlying base wafer2110. Referring to FIG. 22, following a fin etch (as shown in view2202), a plurality of dummy gate structures 2200 may be fabricated and aprocess such as described above may be performed. In an embodiment, thebase stack 2100 is generated by He/H₂ plus cleave based layer transferor growth.

FIG. 23 illustrates cross-sectional views of finalized devicesfabricated either on (a) a silicon substrate or (b) a buried oxidesubstrate, in accordance with an embodiment of the present invention.Referring to part (a) of FIG. 23, the left-hand device represents theinverter structure of FIG. 20 formed on a silicon substrate 2300. Theright-hand device represents the pass gate structure of FIG. 20 formedon a silicon substrate 2300. Referring to part (b) of FIG. 23, theleft-hand device represents the inverter structure of FIG. 20 formed ona buried oxide layer 2302 formed between the device and a siliconsubstrate 2304. The right-hand device represents the pass gate structureof FIG. 20 formed on a buried oxide layer 2302 formed between the deviceand a silicon substrate 2304.

FIG. 24 illustrates cross-sectional views of finalized devicesfabricated with underlying routing layers, in accordance with anembodiment of the present invention. Referring to the left-hand deviceof FIG. 24, the inverter structure of FIG. 20 is shown formed on aburied oxide layer 2400 with power lines 2402 and signal lines 2404formed therein. Referring to the right-hand device of FIG. 24, theinverter structure of FIG. 20 is shown formed on a buried oxide layer2400 with power lines 2402 and signal lines 2404 formed therein.

In other embodiments, exemplary process flows involve construction ofinterconnects on both sides of a device. Flows could be one of, e.g.,layer transfer after IC1 level fabrication, flip and grind flow, implantafter device fabrication, implant prior to device fabrication. In anembodiment, such a process flow implies that power will be deliveredfrom one side of the device stack, but this is not necessary if thepackaging techniques can permit power delivery from both sides of thedevice.

In other embodiments, designs may require a via to connect from thebackside to the front side either for delivering power or signal. In anexample, FIG. 25 shows an example of power being transferred from oneside of a device to the opposite side, in accordance with an embodimentof the present invention.

Referring to FIG. 25, both the source/drain (S/D) and the gate may beconnected to wiring either above or below the devices. In the specificexample shown, a PMOS S/D 2500 and NMOS S/D 2502 are provided. The PMOSS/D 2500 and NMOS S/D 2502 are separated by dielectric 2501 and housedin oxide layer 2503. The PMOS S/D 2500 is coupled to metal line (Vcc)2504 which is coupled to metal via (Vcc) 2506. Metal via 2506 is coupledto additional via 2508 and Vcc wiring 2510. Via 2508 and Vcc wiring 2510are included in dielectric layer 2512. Also included in dielectric layer2512 are VSS lines 2514 and signal line 2516 and via 2518 pairing. Anupper dielectric layer 2520 includes signal lines 2522.

In an embodiment, total chip area scaling can be further enhanced byintegrating more than two transistors vertically either by extending theabove technique, or using layer transfer techniques. In an example, FIG.26 illustrates a cross-sectional view of vertically integrated singlefin elements having interconnect wiring between device layers, inaccordance with an embodiment of the present invention. Referring toFIG. 26, a first device layer 2600 and second device layer 2602 (e.g.,with gates 2602A and fins 2602B) are vertical structures such as thosedescribed above such as described above. One or more metallizationlayers 2604 are between device layers, one or more metallization layers2606 are above, and one or more metallization layers 2608 are below.Each metallization layer may include an interlayer dielectric (ILD)layer 2610, metal lines 2612, vias 2614 and an etch stop layer 2616.Particular routing may include contact 2620 to S/D, contact 2622 togate, and backside to front side via 2624. In an embodiment, such anarchitecture can be fabricated using a layer transfer technique.

FIG. 27 illustrates an approach for extending the above principles to afour device structure technique, in accordance with an embodiment of thepresent invention. Referring to part (a) of FIG. 27, a base stack 2700includes a first silicon layer 2702, a first silicon germanium layer2704, a second silicon layer 2706, a second silicon germanium layer2708, a third silicon layer 2710, a third silicon germanium layer 2712,a fourth silicon layer 2714 and a fourth silicon germanium layer 2716all formed on an underlying base wafer 2718. Referring to part (b) ofFIG. 27, following a fin etch (as shown in view 2750), the silicongermanium layers 2704, 2708, 2712 and 2716 are replaced with an oxidematerial 2728, e.g., through a replacement gate process. Subsequently, apermanent gate structure 2730 may be fabricated. It is to be appreciatedthat the stack may be fabricated either by growing the stack (asdescribed above) or using layer transfer to build the stack.

It is to be appreciated that the structures resulting from the aboveexemplary processing schemes may be used in a same or similar form forsubsequent processing operations to complete circuit elementfabrication. As an example of a completed device, FIGS. 28A and 28Billustrate a cross-sectional view and a plan view (taken along the a-a′axis of the cross-sectional view), respectively, of a non-planarsemiconductor device having a vertical architecture and self-alignedgate edge isolation, in accordance with an embodiment of the presentinvention.

Referring to FIG. 28A, a semiconductor structure or device 2800 includesnon-planar active regions (e.g., a fin structures including protrudingfin portion 2804 and sub-fin region 2805) formed from substrate 2802,and within isolation region 2806. Gate structures 2808 are disposed overthe protruding portions 2804 of the non-planar active regions as well asover a portion of the isolation region 2806. As shown, gate structures2808 include a gate electrode 2850 and a gate dielectric layer 2852. Inone embodiment, although not shown, gate structures 2808 may alsoinclude a dielectric cap layer. Gate structures 2808 are separated byself-aligned gate edge isolation structures 2820. A local interconnect2854 couples adjacent gate structures 2808. A gate contact 2814, andoverlying gate contact via 2816 are also seen from this perspective,along with an overlying metal interconnect 2860, all of which aredisposed in inter-layer dielectric stacks or layers 2870. Also seen fromthe perspective of FIG. 28A, the gate contact 2814 is, in oneembodiment, disposed over the non-planar active regions. As is alsodepicted in FIG. 28A, an interface 2880 exists between a doping profileof protruding fin portions 2804 and sub-fin regions 2805, although otherembodiments do not include such an interface in doping profile betweenthese regions.

In an embodiment, referring again to FIG. 28A, the protruding finportion 2804 is separated into upper and lower fin regions, e.g., by anoxide layer 2899. In an embodiment, referring again to FIG. 28A, thegate structures 2808 are separated into upper and lower gate structures,e.g., at level 2898, which may represent a P/N junction or an insulatinglayer disposed between upper and lower gate electrode regions.

Referring to FIG. 28B, the gate structures 2808 are shown as disposedover the protruding fin portions 2804, as isolated by self-aligned gateedge isolation structures 2820. Source and drain regions 2804A and 2804Bof the protruding fin portions 2804 are shown in this perspective,although it is to be understood that these regions would be overlappedwith trench contact structures. In one embodiment, the source and drainregions 2804A and 2804B are doped portions of original material of theprotruding fin portions 2804. In another embodiment, the material of theprotruding fin portions 2804 is removed and replaced with anothersemiconductor material, e.g., by epitaxial deposition. In either case,the source and drain regions 2804A and 2804B may extend below the heightof dielectric layer 2806, i.e., into the sub-fin region 2805.

In an embodiment, the semiconductor structure or device 2800 is anon-planar device such as, but not limited to, a finFET or a tri-gatedevice. In such an embodiment, a corresponding semiconducting channelregion is composed of or is formed in a three-dimensional body. In onesuch embodiment, the gate structures 2808 surround at least a topsurface and a pair of sidewalls of the three-dimensional body.

Substrate 2802 may be composed of a semiconductor material that canwithstand a manufacturing process and in which charge can migrate. In anembodiment, substrate 2802 is a bulk substrate composed of a crystallinesilicon, silicon/germanium or germanium layer doped with a chargecarrier, such as but not limited to phosphorus, arsenic, boron or acombination thereof, to form active region 2804. In one embodiment, theconcentration of silicon atoms in bulk substrate 2802 is greater than97%. In another embodiment, bulk substrate 2802 is composed of anepitaxial layer grown atop a distinct crystalline substrate, e.g. asilicon epitaxial layer grown atop a boron-doped bulk siliconmono-crystalline substrate. Bulk substrate 2802 may alternatively becomposed of a group III-V material. In an embodiment, bulk substrate2802 is composed of a III-V material such as, but not limited to,gallium nitride, gallium phosphide, gallium arsenide, indium phosphide,indium antimonide, indium gallium arsenide, aluminum gallium arsenide,indium gallium phosphide, or a combination thereof. In one embodiment,bulk substrate 2802 is composed of a III-V material and thecharge-carrier dopant impurity atoms are ones such as, but not limitedto, carbon, silicon, germanium, oxygen, sulfur, selenium or tellurium.

Isolation region 2806 may be composed of a material suitable toultimately electrically isolate, or contribute to the isolation of,portions of a permanent gate structure from an underlying bulk substrateor isolate active regions formed within an underlying bulk substrate,such as isolating fin active regions. For example, in one embodiment,the isolation region 2806 is composed of a dielectric material such as,but not limited to, silicon dioxide, silicon oxy-nitride, siliconnitride, or carbon-doped silicon nitride.

Self-aligned gate edge isolation structures 2820 may be composed of amaterial suitable to ultimately electrically isolate, or contribute tothe isolation of, portions of permanent gate structures from oneanother. For example, in one embodiment, the isolation region 2806 iscomposed of a dielectric material such as, but not limited to, silicondioxide, silicon oxy-nitride, silicon nitride, or carbon-doped siliconnitride.

Gate structures 2808 may be composed of a gate electrode stack, andpossible to vertically stacked gate stacks, which includes a gatedielectric layer 2852 and a gate electrode layer 2850. In an embodiment,the gate electrode of the gate electrode stack is composed of a metalgate and the gate dielectric layer is composed of a high-K material. Forexample, in one embodiment, the gate dielectric layer is composed of amaterial such as, but not limited to, hafnium oxide, hafniumoxy-nitride, hafnium silicate, lanthanum oxide, zirconium oxide,zirconium silicate, tantalum oxide, barium strontium titanate, bariumtitanate, strontium titanate, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, lead zinc niobate, or a combination thereof.Furthermore, a portion of gate dielectric layer may include a layer ofnative oxide formed from the top few layers of the substrate 2802. In anembodiment, the gate dielectric layer is composed of a top high-kportion and a lower portion composed of an oxide of a semiconductormaterial. In one embodiment, the gate dielectric layer is composed of atop portion of hafnium oxide and a bottom portion of silicon dioxide orsilicon oxy-nitride.

In one embodiment, the gate electrode is composed of a metal layer suchas, but not limited to, metal nitrides, metal carbides, metal silicides,metal aluminides, hafnium, zirconium, titanium, tantalum, aluminum,ruthenium, palladium, platinum, cobalt, nickel or conductive metaloxides. In a specific embodiment, the gate electrode is composed of anon-workfunction-setting fill material formed above a metalworkfunction-setting layer.

Spacers associated with the gate electrode stacks may be composed of amaterial suitable to ultimately electrically isolate, or contribute tothe isolation of, a permanent gate structure from adjacent conductivecontacts, such as self-aligned contacts. For example, in one embodiment,the spacers are composed of a dielectric material such as, but notlimited to, silicon dioxide, silicon oxy-nitride, silicon nitride, orcarbon-doped silicon nitride.

Local interconnect 2854, gate contact 2814, and overlying gate contactvia 2816 may be composed of a conductive material. In an embodiment, oneor more of the contacts or vias are composed of a metal species. Themetal species may be a pure metal, such as tungsten, nickel, or cobalt,or may be an alloy such as a metal-metal alloy or a metal-semiconductoralloy (e.g., such as a silicide material). It is to be appreciated thata hardmask layer may be disposed on the local interconnect 2854 inlocations where gate contact 2814 is not located thereon. Furthermore,the local interconnect 2854 may be fabricated by lithographic patterningor, in other embodiments, may be fabricated as a self-alignedinterconnect structure, as aligned with taller versions of aself-aligned gate edge isolation structures 2820.

In an embodiment (although not shown), providing structure 2800 involvesformation of a contact pattern which is essentially perfectly aligned toan existing gate pattern while eliminating the use of a lithographicstep with exceedingly tight registration budget. In one such embodiment,this approach enables the use of intrinsically highly selective wetetching (e.g., versus conventionally implemented dry or plasma etching)to generate contact openings. In an embodiment, a contact pattern isformed by utilizing an existing gate pattern in combination with acontact plug lithography operation. In one such embodiment, the approachenables elimination of the need for an otherwise critical lithographyoperation to generate a contact pattern, as used in conventionalapproaches. In an embodiment, a trench contact grid is not separatelypatterned, but is rather formed between poly (gate) lines. For example,in one such embodiment, a trench contact grid is formed subsequent togate grating patterning but prior to gate grating cuts.

Furthermore, the gate structures 2808 may be fabricated by a replacementgate process. In such a scheme, dummy gate material such as polysiliconor silicon nitride pillar material, may be removed and replaced withpermanent gate electrode material. In one such embodiment, a permanentgate dielectric layer is also formed in this process, as opposed tobeing carried through from earlier processing. In an embodiment, dummygates are removed by a dry etch or wet etch process. In one embodiment,dummy gates are composed of polycrystalline silicon or amorphous siliconand are removed with a dry etch process including use of SF₆. In anotherembodiment, dummy gates are composed of polycrystalline silicon oramorphous silicon and are removed with a wet etch process including useof aqueous NH₄OH or tetramethylammonium hydroxide. In one embodiment,dummy gates are composed of silicon nitride and are removed with a wetetch including aqueous phosphoric acid.

In an embodiment, one or more approaches described herein contemplateessentially a dummy and replacement gate process in combination with adummy and replacement contact process to arrive at structure 2800. Inone such embodiment, the replacement contact process is performed afterthe replacement gate process to allow high temperature anneal of atleast a portion of the permanent gate stack. For example, in a specificsuch embodiment, an anneal of at least a portion of the permanent gatestructures, e.g., after a gate dielectric layer is formed, is performedat a temperature greater than approximately 600 degrees Celsius. Theanneal is performed prior to formation of the permanent contacts.

Referring again to FIG. 28A, in an embodiment, a semiconductor devicehas contact structures that contact portions of a gate electrode formedover an active region. In general, prior to (e.g., in addition to)forming a gate contact structure (such as a via) over an active portionof a gate and in a same layer as a trench contact via, one or moreembodiments of the present invention include first using a gate alignedtrench contact process. Such a process may be implemented to form trenchcontact structures for semiconductor structure fabrication, e.g., forintegrated circuit fabrication. In an embodiment, a trench contactpattern is formed as aligned to an existing gate pattern. By contrast,conventional approaches typically involve an additional lithographyprocess with tight registration of a lithographic contact pattern to anexisting gate pattern in combination with selective contact etches. Forexample, a conventional process may include patterning of a poly (gate)grid with separate patterning of contact features.

FIG. 29 illustrates a computing device 2900 in accordance with oneimplementation of the invention. The computing device 2900 houses aboard 2902. The board 2902 may include a number of components, includingbut not limited to a processor 2904 and at least one communication chip2906. The processor 2904 is physically and electrically coupled to theboard 2902. In some implementations the at least one communication chip2906 is also physically and electrically coupled to the board 2902. Infurther implementations, the communication chip 2906 is part of theprocessor 2904.

Depending on its applications, computing device 2900 may include othercomponents that may or may not be physically and electrically coupled tothe board 2902. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 2906 enables wireless communications for thetransfer of data to and from the computing device 2900. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 2906 may implementany of a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 2900 may include a plurality ofcommunication chips 2906. For instance, a first communication chip 2906may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 2906 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 2904 of the computing device 2900 includes an integratedcircuit die packaged within the processor 2904. In some implementationsof the invention, the integrated circuit die of the processor includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of embodiments of the invention. The term“processor” may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory.

The communication chip 2906 also includes an integrated circuit diepackaged within the communication chip 2906. In accordance with anotherimplementation of embodiments of the invention, the integrated circuitdie of the communication chip includes one or more devices, such asMOS-FET transistors built in accordance with implementations ofembodiments of the invention.

In further implementations, another component housed within thecomputing device 2900 may contain an integrated circuit die thatincludes one or more devices, such as MOS-FET transistors built inaccordance with implementations of embodiments of the invention.

In various implementations, the computing device 2900 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 2900 may be any other electronic device that processes data.

FIG. 30 illustrates an interposer 3000 that includes one or moreembodiments of the invention. The interposer 3000 is an interveningsubstrate used to bridge a first substrate 3002 to a second substrate3004. The first substrate 3002 may be, for instance, an integratedcircuit die. The second substrate 3004 may be, for instance, a memorymodule, a computer motherboard, or another integrated circuit die.Generally, the purpose of an interposer 3000 is to spread a connectionto a wider pitch or to reroute a connection to a different connection.For example, an interposer 3000 may couple an integrated circuit die toa ball grid array (BGA) 3006 that can subsequently be coupled to thesecond substrate 3004. In some embodiments, the first and secondsubstrates 3002/3004 are attached to opposing sides of the interposer3000. In other embodiments, the first and second substrates 3002/3004are attached to the same side of the interposer 3000. And in furtherembodiments, three or more substrates are interconnected by way of theinterposer 3000.

The interposer 3000 may be formed of an epoxy resin, afiberglass-reinforced epoxy resin, a ceramic material, or a polymermaterial such as polyimide. In further implementations, the interposermay be formed of alternate rigid or flexible materials that may includethe same materials described above for use in a semiconductor substrate,such as silicon, germanium, and other group III-V and group IVmaterials.

The interposer may include metal interconnects 3008 and vias 3010,including but not limited to through-silicon vias (TSVs) 3012. Theinterposer 3000 may further include embedded devices 3014, includingboth passive and active devices. Such devices include, but are notlimited to, capacitors, decoupling capacitors, resistors, inductors,fuses, diodes, transformers, sensors, and electrostatic discharge (ESD)devices. More complex devices such as radio-frequency (RF) devices,power amplifiers, power management devices, antennas, arrays, sensors,and MEMS devices may also be formed on the interposer 3000. Inaccordance with embodiments of the invention, apparatuses or processesdisclosed herein may be used in the fabrication of interposer 3000.

Thus, embodiments of the present invention include vertical integrationschemes and circuit elements architectures for area scaling ofsemiconductor devices.

In an embodiment, an inverter structure includes a semiconductor finseparated vertically into an upper region and a lower region. A firstplurality of gate structures is included for controlling the upperregion of the semiconductor fin. A second plurality of gate structuresis included for controlling the lower region of the semiconductor fin.The second plurality of gate structures has a conductivity type oppositethe conductivity type of the first plurality of gate structures.

In one embodiment, the upper region of the fin and the lower region ofthe fin are separated by an insulating layer.

In one embodiment, corresponding ones of the first plurality of gatestructures and the second plurality of gate structures are separated byan insulating layer.

In one embodiment, corresponding ones of the first plurality of gatestructures and the second plurality of gate structures form a P/Njunction.

In one embodiment, the first plurality of gate structures is a pluralityof PMOS gate structures, and the second plurality of gate structures isa plurality of NMOS gate structures.

In one embodiment, the first plurality of gate structures is disposedover a top surface of the semiconductor fin and along sidewalls of theupper region of the semiconductor fin, and the second plurality of gatestructures is disposed along sidewalls of the lower region of thesemiconductor fin.

In one embodiment, the second plurality of gate structures is furtherdisposed below a bottom surface of the semiconductor fin.

In an embodiment, a pass gate structure includes a semiconductor finseparated vertically into an upper region and a lower region. A firstplurality of gate structures is included for controlling the upperregion of the semiconductor fin. A second plurality of gate structuresis included for controlling the lower region of the semiconductor fin.The second plurality of gate structures has a same conductivity type asthe conductivity type of the first plurality of gate structures.

In one embodiment, the upper region of the fin and the lower region ofthe fin are separated by an insulating layer.

In one embodiment, corresponding ones of the first plurality of gatestructures and the second plurality of gate structures are separated byan insulating layer.

In one embodiment, the first plurality of gate structures is a pluralityof NMOS gate structures, and the second plurality of gate structures isa plurality of NMOS gate structures.

In one embodiment, the first plurality of gate structures is disposedover a top surface of the semiconductor fin and along sidewalls of theupper region of the semiconductor fin, and the second plurality of gatestructures is disposed along sidewalls of the lower region of thesemiconductor fin.

In one embodiment, the second plurality of gate structures is furtherdisposed below a bottom surface of the semiconductor fin.

In an embodiment, a method of fabricating a circuit element on a singlesemiconductor fin includes forming a semiconductor fin. The method alsoincludes separating the semiconductor fin vertically into an upperregion and a lower region. The method also includes forming a lowerplurality of gate structures for controlling the lower region of thesemiconductor fin. The method also includes forming an upper pluralityof gate structures for controlling the upper region of the semiconductorfin.

In one embodiment, forming the upper plurality of gate structuresincludes forming a plurality of gate structures having a conductivitytype opposite the conductivity type of the lower plurality of gatestructures.

In one embodiment, forming the upper plurality of gate structuresincludes forming a plurality of gate structures having a sameconductivity type as the conductivity type of the lower plurality ofgate structures.

In one embodiment, separating the semiconductor fin vertically into anupper region and a lower region includes forming an oxide layer betweenthe upper region and the lower region of the semiconductor fin.

In one embodiment, forming an oxide layer between the upper region andthe lower region of the semiconductor fin includes selectively removinga portion of a silicon germanium layer from between upper and lowersilicon layers of the semiconductor fin.

In one embodiment, the method further includes forming first epitaxialsource and drain regions for the lower portion of the semiconductor fin,and forming second epitaxial source and drain regions for the upperportion of the semiconductor fin, the second epitaxial source and drainregions of opposite conductivity type to the first epitaxial source anddrain regions.

In one embodiment, the method further includes forming first epitaxialsource and drain regions for the lower portion of the semiconductor fin,and forming second epitaxial source and drain regions for the upperportion of the semiconductor fin, the second epitaxial source and drainregions of a same conductivity type as the first epitaxial source anddrain regions.

In one embodiment, forming the lower plurality of gate structures andforming the upper plurality of gate structures includes using areplacement gate process.

What is claimed is:
 1. An inverter structure, comprising: asemiconductor fin separated vertically into an upper region and a lowerregion; a first plurality of gate structures for controlling the upperregion of the semiconductor fin; and a second plurality of gatestructures for controlling the lower region of the semiconductor fin,the second plurality of gate structures having a conductivity typeopposite the conductivity type of the first plurality of gatestructures.
 2. The inverter structure of claim 1, wherein the upperregion of the fin and the lower region of the fin are separated by aninsulating layer.
 3. The inverter structure of claim 1, whereincorresponding ones of the first plurality of gate structures and thesecond plurality of gate structures are separated by an insulatinglayer.
 4. The inverter structure of claim 1, wherein corresponding onesof the first plurality of gate structures and the second plurality ofgate structures form a P/N junction.
 5. The inverter structure of claim1, wherein the first plurality of gate structures is a plurality of PMOSgate structures, and the second plurality of gate structures is aplurality of NMOS gate structures.
 6. The inverter structure of claim 1,wherein the first plurality of gate structures is disposed over a topsurface of the semiconductor fin and along sidewalls of the upper regionof the semiconductor fin, and wherein the second plurality of gatestructures is disposed along sidewalls of the lower region of thesemiconductor fin.
 7. The inverter structure of claim 6, wherein thesecond plurality of gate structures is further disposed below a bottomsurface of the semiconductor fin.
 8. A pass gate structure, comprising:a semiconductor fin separated vertically into an upper region and alower region; a first plurality of gate structures for controlling theupper region of the semiconductor fin; and a second plurality of gatestructures for controlling the lower region of the semiconductor fin,the second plurality of gate structures having a same conductivity typeas the conductivity type of the first plurality of gate structures. 9.The inverter structure of claim 8, wherein the upper region of the finand the lower region of the fin are separated by an insulating layer.10. The inverter structure of claim 8, wherein corresponding ones of thefirst plurality of gate structures and the second plurality of gatestructures are separated by an insulating layer.
 11. The inverterstructure of claim 8, wherein the first plurality of gate structures isa plurality of NMOS gate structures, and the second plurality of gatestructures is a plurality of NMOS gate structures.
 12. The inverterstructure of claim 8, wherein the first plurality of gate structures isdisposed over a top surface of the semiconductor fin and along sidewallsof the upper region of the semiconductor fin, and wherein the secondplurality of gate structures is disposed along sidewalls of the lowerregion of the semiconductor fin.
 13. The inverter structure of claim 12,wherein the second plurality of gate structures is further disposedbelow a bottom surface of the semiconductor fin.
 14. A method offabricating a circuit element on a single semiconductor fin, the methodcomprising: forming a semiconductor fin; separating the semiconductorfin vertically into an upper region and a lower region; forming a lowerplurality of gate structures for controlling the lower region of thesemiconductor fin; and forming an upper plurality of gate structures forcontrolling the upper region of the semiconductor fin.
 15. The method ofclaim 14, wherein forming the upper plurality of gate structurescomprises forming a plurality of gate structures having a conductivitytype opposite the conductivity type of the lower plurality of gatestructures.
 16. The method of claim 14, wherein forming the upperplurality of gate structures comprises forming a plurality of gatestructures having a same conductivity type as the conductivity type ofthe lower plurality of gate structures.
 17. The method of claim 14,wherein separating the semiconductor fin vertically into an upper regionand a lower region comprises forming an oxide layer between the upperregion and the lower region of the semiconductor fin.
 18. The method ofclaim 17, wherein forming an oxide layer between the upper region andthe lower region of the semiconductor fin comprises selectively removinga portion of a silicon germanium layer from between upper and lowersilicon layers of the semiconductor fin.
 19. The method of claim 14,further comprising: forming first epitaxial source and drain regions forthe lower portion of the semiconductor fin; and forming second epitaxialsource and drain regions for the upper portion of the semiconductor fin,the second epitaxial source and drain regions of opposite conductivitytype to the first epitaxial source and drain regions.
 20. The method ofclaim 14, further comprising: forming first epitaxial source and drainregions for the lower portion of the semiconductor fin; and formingsecond epitaxial source and drain regions for the upper portion of thesemiconductor fin, the second epitaxial source and drain regions of asame conductivity type as the first epitaxial source and drain regions.21. The method of claim 14, wherein forming the lower plurality of gatestructures and forming the upper plurality of gate structures comprisesusing a replacement gate process.